!--------------------------------------------------------------------------------------------------!
!   CP2K: A general program to perform molecular dynamics simulations                              !
!   Copyright 2000-2024 CP2K developers group <https://cp2k.org>                                   !
!                                                                                                  !
!   SPDX-License-Identifier: GPL-2.0-or-later                                                      !
!--------------------------------------------------------------------------------------------------!

! **************************************************************************************************
!> \par History
!>      - taken out of input_cp2k_motion
!> \author teo & fawzi
! **************************************************************************************************
MODULE input_cp2k_colvar
   USE bibliography,                    ONLY: Branduardi2007
   USE colvar_types,                    ONLY: &
        do_clv_fix_point, do_clv_geo_center, do_clv_x, do_clv_xy, do_clv_xyz, do_clv_xz, do_clv_y, &
        do_clv_yz, do_clv_z, plane_def_atoms, plane_def_vec
   USE cp_output_handling,              ONLY: add_last_numeric,&
                                              cp_print_key_section_create,&
                                              high_print_level,&
                                              low_print_level
   USE cp_units,                        ONLY: cp_unit_to_cp2k
   USE input_constants,                 ONLY: gaussian,&
                                              numerical,&
                                              rmsd_all,&
                                              rmsd_list,&
                                              rmsd_weightlist
   USE input_keyword_types,             ONLY: keyword_create,&
                                              keyword_release,&
                                              keyword_type
   USE input_section_types,             ONLY: section_add_keyword,&
                                              section_add_subsection,&
                                              section_create,&
                                              section_release,&
                                              section_type
   USE input_val_types,                 ONLY: char_t,&
                                              integer_t,&
                                              lchar_t,&
                                              real_t
   USE kinds,                           ONLY: dp
   USE string_utilities,                ONLY: s2a
#include "./base/base_uses.f90"

   IMPLICIT NONE
   PRIVATE

   LOGICAL, PRIVATE, PARAMETER :: debug_this_module = .FALSE.
   CHARACTER(len=*), PARAMETER, PRIVATE :: moduleN = 'input_cp2k_colvar'

   PUBLIC :: create_colvar_section, &
             create_colvar_xyz_d_section, &
             create_colvar_xyz_od_section

CONTAINS

! **************************************************************************************************
!> \brief creates the colvar section
!> \param section the section to be created
!> \param skip_recursive_colvar ...
!> \author teo
! **************************************************************************************************
   RECURSIVE SUBROUTINE create_colvar_section(section, skip_recursive_colvar)
      TYPE(section_type), POINTER                        :: section
      LOGICAL, OPTIONAL                                  :: skip_recursive_colvar

      LOGICAL                                            :: skip
      TYPE(section_type), POINTER                        :: print_key, subsection

      skip = .FALSE.
      IF (PRESENT(skip_recursive_colvar)) skip = skip_recursive_colvar
      CPASSERT(.NOT. ASSOCIATED(section))
      CALL section_create(section, __LOCATION__, name="COLVAR", &
                          description="This section specifies the nature of the collective variables.", &
                          n_keywords=1, n_subsections=1, repeats=.TRUE.)
      NULLIFY (subsection, print_key)

      CALL create_colvar_var_section(subsection=subsection, &
                                     section=section, skip_recursive_colvar=skip)

      CALL section_create(subsection, __LOCATION__, name="PRINT", &
                          description="Controls the printing of the colvar specifications", &
                          n_keywords=0, n_subsections=1, repeats=.TRUE.)
      NULLIFY (print_key)
      CALL cp_print_key_section_create(print_key, __LOCATION__, "PROGRAM_RUN_INFO", &
                                       description="Controls the printing of basic information during colvar setup.", &
                                       print_level=low_print_level, add_last=add_last_numeric, filename="__STD_OUT__")
      CALL section_add_subsection(subsection, print_key)
      CALL section_release(print_key)
      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

      CALL create_clv_info_section(subsection)
      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

   END SUBROUTINE create_colvar_section

! **************************************************************************************************
!> \brief Create the restart section for colvar restraints
!>      This section will be only used for restraint restarts.
!>      Constraints are handled automatically
!> \param section the section to create
!> \author Teodoro Laino 08.2006
! **************************************************************************************************
   SUBROUTINE create_clv_info_section(section)
      TYPE(section_type), POINTER                        :: section

      TYPE(keyword_type), POINTER                        :: keyword

      CPASSERT(.NOT. ASSOCIATED(section))
      NULLIFY (keyword)
      CALL section_create(section, __LOCATION__, name="COLVAR_FUNC_INFO", &
                          description="Specify further data possibly used by colvars, depending "// &
                          "on the starting geometry, for computing the functions value.", &
                          n_subsections=0, repeats=.FALSE.)

      CALL keyword_create(keyword, __LOCATION__, name="_DEFAULT_KEYWORD_", &
                          description="Colvar function data."// &
                          " The order is an internal order. So if you decide to edit/modify/add these values by hand"// &
                          " you should know very well what you are doing.!", repeats=.TRUE., &
                          usage="{Real} ...", type_of_var=real_t, n_var=-1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

   END SUBROUTINE create_clv_info_section

! **************************************************************************************************
!> \brief creates the collective variables for the colvar section
!> \param subsection ...
!> \param section the section to be created
!> \param skip_recursive_colvar ...
!> \author teo
! **************************************************************************************************
   RECURSIVE SUBROUTINE create_colvar_var_section(subsection, section, skip_recursive_colvar)
      TYPE(section_type), POINTER                        :: subsection, section
      LOGICAL, INTENT(IN)                                :: skip_recursive_colvar

      CPASSERT(.NOT. ASSOCIATED(subsection))
      CPASSERT(ASSOCIATED(section))

      CALL create_colvar_dist_section(subsection)
      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

      CALL create_colvar_angle_section(subsection)
      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

      CALL create_colvar_torsion_section(subsection)
      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

      CALL create_colvar_coord_section(subsection)
      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

      CALL create_colvar_pop_section(subsection)
      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

      CALL create_colvar_gyr_section(subsection)
      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

      CALL create_colvar_d_pl_section(subsection)
      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

      CALL create_colvar_a_pl_section(subsection)
      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

      CALL create_colvar_rot_section(subsection)
      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

      CALL create_colvar_dfunct_section(subsection)
      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

      CALL create_colvar_qparm_section(subsection)
      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

      CALL create_colvar_hydronium_shell_section(subsection)
      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

      CALL create_colvar_hydronium_dist_section(subsection)
      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

      CALL create_colvar_acid_hyd_dist_section(subsection)
      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

      CALL create_colvar_acid_hyd_shell_section(subsection)
      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

      CALL create_colvar_rmsd_section(subsection)
      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

      CALL create_colvar_xyz_d_section(subsection)
      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

      CALL create_colvar_xyz_od_section(subsection)
      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

      CALL create_colvar_u_section(subsection)
      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

      CALL create_colvar_wc_section(subsection)
      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

      CALL create_colvar_hbp_section(subsection)
      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

      CALL create_colvar_ring_puckering_section(subsection)
      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

      CALL create_colvar_cond_dist_section(subsection)
      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

      IF (.NOT. skip_recursive_colvar) THEN
         CALL create_colvar_rpath_section(subsection)
         CALL section_add_subsection(section, subsection)
         CALL section_release(subsection)

         CALL create_colvar_dpath_section(subsection)
         CALL section_add_subsection(section, subsection)
         CALL section_release(subsection)

         CALL create_colvar_comb_section(subsection)
         CALL section_add_subsection(section, subsection)
         CALL section_release(subsection)
      END IF

   END SUBROUTINE create_colvar_var_section

! **************************************************************************************************
!> \brief collective variables specifying coordination
!> \param section the section to be created
!> \author teo
! **************************************************************************************************
   SUBROUTINE create_colvar_coord_section(section)
      TYPE(section_type), POINTER                        :: section

      TYPE(keyword_type), POINTER                        :: keyword
      TYPE(section_type), POINTER                        :: subsection

      CPASSERT(.NOT. ASSOCIATED(section))
      CALL section_create(section, __LOCATION__, name="coordination", &
                          description="Section to define the coordination number as a collective variable.", &
                          n_keywords=1, n_subsections=0, repeats=.FALSE.)

      NULLIFY (subsection, keyword)

      CALL keyword_create(keyword, __LOCATION__, name="ATOMS_FROM", &
                          variants=(/"POINTS_FROM"/), &
                          description="Specify indexes of atoms/points building the coordination variable. ", &
                          usage="ATOMS_FROM {integer} {integer} ..", repeats=.TRUE., &
                          n_var=-1, type_of_var=integer_t)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="ATOMS_TO", &
                          variants=(/"POINTS_TO"/), &
                          description="Specify indexes of atoms/points building the coordination variable. ", &
                          usage="ATOMS_TO {integer} {integer} ..", repeats=.TRUE., &
                          n_var=-1, type_of_var=integer_t)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="ATOMS_TO_B", &
                          variants=(/"POINTS_TO_B"/), &
                          description="For the CV given by the multiplication of two coorination numbers,"// &
                          " here specify indexes of the third set of atoms/points. ", &
                          usage="ATOMS_TO_B {integer} {integer} ..", repeats=.TRUE., &
                          n_var=-1, type_of_var=integer_t)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="KINDS_FROM", &
                          description="Specify alternatively kinds of atoms building the coordination variable.", &
                          usage="KINDS_FROM {CHAR} {CHAR} ..", repeats=.TRUE., &
                          n_var=-1, type_of_var=char_t)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="KINDS_TO", &
                          description="Specify alternatively kinds of atoms building the coordination variable.", &
                          usage="KINDS_TO {CHAR} {CHAR} ..", repeats=.TRUE., &
                          n_var=-1, type_of_var=char_t)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="KINDS_TO_B", &
                          description="For the CV given by the multiplication of two coorination numbers,"// &
                          " here specify alternatively kinds of atoms building the coordination variable.", &
                          usage="KINDS_TO_B {CHAR} {CHAR} ..", repeats=.TRUE., &
                          n_var=-1, type_of_var=char_t)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      ! Must be present in each colvar and handled properly
      CALL create_point_section(subsection)
      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

      CALL keyword_create(keyword, __LOCATION__, name="R0", &
                          variants=(/"R_0"/), &
                          description="Specify the R0 parameter in the coordination function.", &
                          usage="R0 {real}", default_r_val=3.0_dp, &
                          unit_str="bohr", n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="NN", &
                          variants=(/"EXPON_NUMERATOR"/), &
                          description="Sets the value of the numerator of the exponential factor"// &
                          " in the coordination FUNCTION.", &
                          usage="NN {integer}", default_i_val=6, &
                          n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="ND", &
                          variants=(/"EXPON_DENOMINATOR"/), &
                          description="Sets the value of the denominator of the exponential factor"// &
                          " in the coordination FUNCTION.", &
                          usage="ND {integer}", default_i_val=12, &
                          n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="R0_B", &
                          variants=(/"R_0_B"/), &
                          description="For the CV given by the multiplication of two coorination numbers,"// &
                          " specify the R0 parameter in the second coordination function.", &
                          usage="R0_B {real}", default_r_val=3.0_dp, &
                          unit_str="bohr", n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="NN_B", &
                          variants=(/"EXPON_NUMERATOR_B"/), &
                          description="For the CV given by the multiplication of two coorination numbers,"// &
                          " Sets the value of the numerator of the exponential factor"// &
                          " in the coordination FUNCTION.", &
                          usage="NN_B {integer}", default_i_val=6, &
                          n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="ND_B", &
                          variants=(/"EXPON_DENOMINATOR_B"/), &
                          description="For the CV given by the multiplication of two coorination numbers,"// &
                          " Sets the value of the denominator of the exponential factor"// &
                          " in the coordination FUNCTION.", &
                          usage="ND_B {integer}", default_i_val=12, &
                          n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

   END SUBROUTINE create_colvar_coord_section

! **************************************************************************************************
!> \brief ...
!> \param section ...
! **************************************************************************************************
   SUBROUTINE create_colvar_cond_dist_section(section)
      TYPE(section_type), POINTER                        :: section

      TYPE(keyword_type), POINTER                        :: keyword
      TYPE(section_type), POINTER                        :: subsection

      CPASSERT(.NOT. ASSOCIATED(section))
      CALL section_create(section, __LOCATION__, name="CONDITIONED_DISTANCE", &
                          description="Section to define the conditioned distance as a collective variable.", &
                          n_keywords=1, n_subsections=0, repeats=.FALSE.)

      NULLIFY (subsection, keyword)

      CALL keyword_create(keyword, __LOCATION__, name="ATOMS_DISTANCE", &
                          description="Specify indexes of atoms/points from which the distance is computed. ", &
                          usage="ATOMS_DISTANCE {integer} {integer} ..", repeats=.TRUE., &
                          n_var=-1, type_of_var=integer_t)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="ATOMS_FROM", &
                          variants=(/"POINTS_FROM"/), &
                          description="Specify indexes of atoms/points building the coordination variable. ", &
                          usage="ATOMS_FROM {integer} {integer} ..", repeats=.TRUE., &
                          n_var=-1, type_of_var=integer_t)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="ATOMS_TO", &
                          variants=(/"POINTS_TO"/), &
                          description="Specify indexes of atoms/points building the coordination variable. ", &
                          usage="ATOMS_TO {integer} {integer} ..", repeats=.TRUE., &
                          n_var=-1, type_of_var=integer_t)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="KINDS_FROM", &
                          description="Specify alternatively kinds of atoms building the coordination variable.", &
                          usage="KINDS_FROM {CHAR} {CHAR} ..", repeats=.TRUE., &
                          n_var=-1, type_of_var=char_t)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="KINDS_TO", &
                          description="Specify alternatively kinds of atoms building the coordination variable.", &
                          usage="KINDS_TO {CHAR} {CHAR} ..", repeats=.TRUE., &
                          n_var=-1, type_of_var=char_t)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      ! Must be present in each colvar and handled properly
      CALL create_point_section(subsection)
      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

      CALL keyword_create(keyword, __LOCATION__, name="R0", &
                          variants=(/"R_0"/), &
                          description="Specify the R0 parameter in the coordination function.", &
                          usage="R0 {real}", default_r_val=3.0_dp, &
                          unit_str="bohr", n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="NN", &
                          variants=(/"EXPON_NUMERATOR"/), &
                          description="Sets the value of the numerator of the exponential factor"// &
                          " in the coordination FUNCTION.", &
                          usage="NN {integer}", default_i_val=6, &
                          n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="ND", &
                          variants=(/"EXPON_DENOMINATOR"/), &
                          description="Sets the value of the denominator of the exponential factor"// &
                          " in the coordination FUNCTION.", &
                          usage="ND {integer}", default_i_val=12, &
                          n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="LAMBDA", &
                          description="Specify the lambda parameter at the exponent of the conditioned distance function.", &
                          usage="R0 {real}", default_r_val=3.0_dp, &
                          unit_str="bohr", n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

   END SUBROUTINE create_colvar_cond_dist_section

! **************************************************************************************************
!> \brief collective variables specifying population of a specie based on coordination
!> \param section the section to be created
!> \date  01.2009
!> \author Fabio Sterpone
! **************************************************************************************************
   SUBROUTINE create_colvar_pop_section(section)
      TYPE(section_type), POINTER                        :: section

      TYPE(keyword_type), POINTER                        :: keyword
      TYPE(section_type), POINTER                        :: subsection

      CPASSERT(.NOT. ASSOCIATED(section))
      CALL section_create(section, __LOCATION__, name="population", &
                          description="Section to define the population of specie as a collective variable. "// &
                          "See also <https://doi.org/10.1021/jp3019588>.", &
                          n_keywords=1, n_subsections=0, repeats=.FALSE.)

      NULLIFY (subsection, keyword)

      CALL keyword_create(keyword, __LOCATION__, name="ATOMS_FROM", &
                          variants=(/"POINTS_FROM"/), &
                          description="Specify indexes of atoms/points building the coordination variable. ", &
                          usage="ATOMS_FROM {integer} {integer} ..", repeats=.TRUE., &
                          n_var=-1, type_of_var=integer_t)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="ATOMS_TO", &
                          variants=(/"POINTS_TO"/), &
                          description="Specify indexes of atoms/points building the coordination variable. ", &
                          usage="ATOMS_TO {integer} {integer} ..", repeats=.TRUE., &
                          n_var=-1, type_of_var=integer_t)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="KINDS_FROM", &
                          description="Specify alternatively kinds of atoms building the coordination variable.", &
                          usage="KINDS_FROM {CHAR} {CHAR} ..", repeats=.TRUE., &
                          n_var=-1, type_of_var=char_t)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="KINDS_TO", &
                          description="Specify alternatively kinds of atoms building the coordination variable.", &
                          usage="KINDS_TO {CHAR} {CHAR} ..", repeats=.TRUE., &
                          n_var=-1, type_of_var=char_t)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      ! Must be present in each colvar and handled properly
      CALL create_point_section(subsection)
      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

      CALL keyword_create(keyword, __LOCATION__, name="R0", &
                          variants=(/"R_0"/), &
                          description="Specify the R0 parameter in the coordination function.", &
                          usage="R0 {real}", default_r_val=3.0_dp, &
                          n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="NN", &
                          variants=(/"EXPON_NUMERATOR"/), &
                          description="Sets the value of the numerator of the exponential factor"// &
                          " in the coordination FUNCTION.", &
                          usage="NN {integer}", default_i_val=6, &
                          n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="ND", &
                          variants=(/"EXPON_DENOMINATOR"/), &
                          description="Sets the value of the denominator of the exponential factor"// &
                          " in the coordination FUNCTION.", &
                          usage="ND {integer}", default_i_val=12, &
                          n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="n0", &
                          variants=(/"n_0"/), &
                          description="Specify the n0 parameter that sets the coordination of the species.", &
                          usage="n0 {integer}", default_i_val=4, &
                          n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="SIGMA", &
                          description="Specify the gaussian width of used to build the population istogram.", &
                          usage="SIGMA {real}", default_r_val=0.5_dp, &
                          n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

   END SUBROUTINE create_colvar_pop_section

! **************************************************************************************************
!> \brief ...
!> \param section ...
! **************************************************************************************************
   SUBROUTINE create_colvar_gyr_section(section)
      TYPE(section_type), POINTER                        :: section

      TYPE(keyword_type), POINTER                        :: keyword
      TYPE(section_type), POINTER                        :: subsection

      CPASSERT(.NOT. ASSOCIATED(section))
      CALL section_create(section, __LOCATION__, name="GYRATION_RADIUS", &
                          description="Section to define the gyration radius as a collective variable.", &
                          n_keywords=1, n_subsections=0, repeats=.FALSE.)

      NULLIFY (subsection, keyword)

      CALL keyword_create(keyword, __LOCATION__, name="ATOMS", &
                          variants=(/"POINTS"/), &
                          description="Specify indexes of atoms/points defyining the gyration radius variable. ", &
                          usage="ATOMS {integer} {integer} ..", repeats=.TRUE., &
                          n_var=-1, type_of_var=integer_t)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="KINDS", &
                          description="Specify alternatively kinds of atoms defining the gyration radius.", &
                          usage="KINDS {CHAR} {CHAR} ..", repeats=.TRUE., &
                          n_var=-1, type_of_var=char_t)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      ! Must be present in each colvar and handled properly
      CALL create_point_section(subsection)
      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

   END SUBROUTINE create_colvar_gyr_section

! **************************************************************************************************
!> \brief collective variables specifying torsion
!> \param section the section to be created
!> \author teo
! **************************************************************************************************
   SUBROUTINE create_colvar_dfunct_section(section)
      TYPE(section_type), POINTER                        :: section

      TYPE(keyword_type), POINTER                        :: keyword
      TYPE(section_type), POINTER                        :: subsection

      CPASSERT(.NOT. ASSOCIATED(section))
      CALL section_create(section, __LOCATION__, name="DISTANCE_FUNCTION", &
                          description="Section to define functions between two distances as collective variables."// &
                          " The function is defined as d1+coeff*d2", &
                          n_keywords=1, n_subsections=0, repeats=.FALSE.)

      NULLIFY (keyword, subsection)

      CALL keyword_create(keyword, __LOCATION__, name="ATOMS", &
                          variants=(/"POINTS"/), &
                          description="Specifies the indexes of atoms/points for the two bonds d1=(1-2) d2=(3-4).", &
                          usage="ATOMS {integer} {integer} {integer} {integer}", &
                          n_var=4, type_of_var=integer_t)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="COEFFICIENT", &
                          description="Specifies the coefficient in the function for the constraint."// &
                          " -1.0 has to be used for distance difference, 1.0 for distance addition", &
                          usage="COEFFICIENT {real}", &
                          type_of_var=real_t)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="PBC", &
                          description="Whether periodic boundary conditions should be applied on the "// &
                          "atomic position before computing the colvar or not.", &
                          usage="PBC", &
                          default_l_val=.TRUE., lone_keyword_l_val=.TRUE.)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      ! Must be present in each colvar and handled properly
      CALL create_point_section(subsection)
      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

   END SUBROUTINE create_colvar_dfunct_section

! **************************************************************************************************
!> \brief collective variables specifying torsion
!> \param section the section to be created
!> \author teo
! **************************************************************************************************
   SUBROUTINE create_colvar_torsion_section(section)
      TYPE(section_type), POINTER                        :: section

      TYPE(keyword_type), POINTER                        :: keyword
      TYPE(section_type), POINTER                        :: subsection

      CPASSERT(.NOT. ASSOCIATED(section))
      CALL section_create(section, __LOCATION__, name="torsion", &
                          description="Section to define the torsion as a collective variables.", &
                          n_keywords=1, n_subsections=0, repeats=.FALSE.)

      NULLIFY (keyword, subsection)

      CALL keyword_create(keyword, __LOCATION__, name="ATOMS", &
                          variants=(/"POINTS"/), &
                          description="Specifies the indexes of atoms/points defining the torsion.", &
                          usage="ATOMS {integer} {integer} {integer} {integer}", &
                          n_var=4, type_of_var=integer_t)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      ! Must be present in each colvar and handled properly
      CALL create_point_section(subsection)
      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

   END SUBROUTINE create_colvar_torsion_section

! **************************************************************************************************
!> \brief collective variables specifying torsion
!> \param section the section to be created
!> \author teo
! **************************************************************************************************
   SUBROUTINE create_colvar_rot_section(section)
      TYPE(section_type), POINTER                        :: section

      TYPE(keyword_type), POINTER                        :: keyword
      TYPE(section_type), POINTER                        :: subsection

      CPASSERT(.NOT. ASSOCIATED(section))
      CALL section_create(section, __LOCATION__, name="bond_rotation", &
                          description="Section to define the rotation of a bond/line with respect to"// &
                          " another bond/line", &
                          n_keywords=1, n_subsections=0, repeats=.FALSE.)

      NULLIFY (keyword, subsection)

      CALL keyword_create(keyword, __LOCATION__, name="P1_BOND1", &
                          description="Specifies the index of atom/point defining the first point"// &
                          " of the first bond/line.", &
                          usage="P1_BOND1 {integer}", &
                          n_var=1, type_of_var=integer_t)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="P2_BOND1", &
                          description="Specifies the index of atom/point defining the second point"// &
                          " of the first bond/line.", &
                          usage="P2_BOND1 {integer}", &
                          n_var=1, type_of_var=integer_t)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="P1_BOND2", &
                          description="Specifies the index of atom/point defining the first point"// &
                          " of the second bond/line.", &
                          usage="P1_BOND2 {integer}", &
                          n_var=1, type_of_var=integer_t)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="P2_BOND2", &
                          description="Specifies the index of atom/point defining the second point"// &
                          " of the second bond/line.", &
                          usage="P2_BOND2 {integer}", &
                          n_var=1, type_of_var=integer_t)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      ! Must be present in each colvar and handled properly
      CALL create_point_section(subsection)
      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

   END SUBROUTINE create_colvar_rot_section

! **************************************************************************************************
!> \brief collective variables specifying angles
!> \param section the section to be created
!> \author teo
! **************************************************************************************************
   SUBROUTINE create_colvar_angle_section(section)
      TYPE(section_type), POINTER                        :: section

      TYPE(keyword_type), POINTER                        :: keyword
      TYPE(section_type), POINTER                        :: subsection

      CPASSERT(.NOT. ASSOCIATED(section))
      CALL section_create(section, __LOCATION__, name="angle", &
                          description="Section to define the angle as a collective variables.", &
                          n_keywords=1, n_subsections=0, repeats=.FALSE.)
      NULLIFY (keyword, subsection)

      CALL keyword_create(keyword, __LOCATION__, name="ATOMS", &
                          variants=(/"POINTS"/), &
                          description="Specifies the indexes of atoms/points defining the angle.", &
                          usage="ATOMS {integer} {integer} {integer}", &
                          n_var=3, type_of_var=integer_t)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      ! Must be present in each colvar and handled properly
      CALL create_point_section(subsection)
      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

   END SUBROUTINE create_colvar_angle_section

! **************************************************************************************************
!> \brief creates the colvar section regarded to the collective variables dist
!> \param section the section to be created
!> \author teo
! **************************************************************************************************
   SUBROUTINE create_colvar_dist_section(section)
      TYPE(section_type), POINTER                        :: section

      TYPE(keyword_type), POINTER                        :: keyword
      TYPE(section_type), POINTER                        :: subsection

      CPASSERT(.NOT. ASSOCIATED(section))
      CALL section_create(section, __LOCATION__, name="distance", &
                          description="Section to define the distance as a collective variables.", &
                          n_keywords=1, n_subsections=0, repeats=.FALSE.)
      NULLIFY (keyword, subsection)

      CALL keyword_create(keyword, __LOCATION__, name="ATOMS", &
                          variants=(/"POINTS"/), &
                          description="Specifies the indexes of atoms/points defining the distance.", &
                          usage="ATOMS {integer} {integer}", &
                          n_var=2, type_of_var=integer_t)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)
      CALL keyword_create(keyword, __LOCATION__, name="AXIS", &
                          description="Define the axes along which the colvar should be evaluated", &
                          usage="AXIS (XYZ | X | Y | Z | XY| XZ | YZ)", &
                          enum_c_vals=s2a("XYZ", "X", "Y", "Z", "XY", "XZ", "YZ"), &
                          enum_i_vals=(/do_clv_xyz, do_clv_x, do_clv_y, do_clv_z, do_clv_xy, do_clv_xz, do_clv_yz/), &
                          default_i_val=do_clv_xyz)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="SIGN", &
                          description="Whether the distance along one Cartesian axis has to be considered with sign."// &
                          " This option is valid if only one dimension is selected.", &
                          usage="SIGN", &
                          default_l_val=.FALSE., lone_keyword_l_val=.TRUE.)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      ! Must be present in each colvar and handled properly
      CALL create_point_section(subsection)
      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

   END SUBROUTINE create_colvar_dist_section

! **************************************************************************************************
!> \brief creates the colvar section regarded to the collective variables dist
!> \param section the section to be created
!> \author teo
! **************************************************************************************************
   SUBROUTINE create_colvar_xyz_d_section(section)
      TYPE(section_type), POINTER                        :: section

      TYPE(keyword_type), POINTER                        :: keyword
      TYPE(section_type), POINTER                        :: subsection

      CPASSERT(.NOT. ASSOCIATED(section))
      CALL section_create(section, __LOCATION__, name="XYZ_DIAG", &
                          description="Section to define the distance of an atom from its starting "// &
                          "position ((X-X(0))^2+(Y-Y(0))^2+(Z-Z(0))^2) or part of its components as a collective variable. "// &
                          "If absolute_position is specified, instead the CV is represented by the "// &
                          "instantaneous position of the atom (only available for X, Y or Z components).", &
                          n_keywords=1, n_subsections=0, repeats=.FALSE.)
      NULLIFY (keyword, subsection)

      CALL keyword_create(keyword, __LOCATION__, name="ATOM", &
                          variants=(/"POINT"/), &
                          description="Specifies the index of the atom/point.", &
                          usage="ATOM {integer}", &
                          n_var=1, type_of_var=integer_t)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="COMPONENT", &
                          description="Define the component of the position vector which will be used "// &
                          "as a colvar.", &
                          usage="AXIS (XYZ | X | Y | Z | XY| XZ | YZ)", &
                          enum_c_vals=s2a("XYZ", "X", "Y", "Z", "XY", "XZ", "YZ"), &
                          enum_i_vals=(/do_clv_xyz, do_clv_x, do_clv_y, do_clv_z, do_clv_xy, do_clv_xz, do_clv_yz/), &
                          default_i_val=do_clv_xyz)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="PBC", &
                          description="Whether periodic boundary conditions should be applied on the "// &
                          "atomic position before computing the colvar or not.", &
                          usage="PBC", &
                          default_l_val=.TRUE., lone_keyword_l_val=.TRUE.)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="ABSOLUTE_POSITION", &
                          description="If enabled, the absolute position of the atoms will be used. ", &
                          usage="ABSOLUTE_POSITION", &
                          default_l_val=.FALSE., lone_keyword_l_val=.TRUE.)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      ! Must be present in each colvar and handled properly
      CALL create_point_section(subsection)
      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

   END SUBROUTINE create_colvar_xyz_d_section

! **************************************************************************************************
!> \brief creates the colvar section regarded to the collective variables dist
!> \param section the section to be created
!> \author teo
! **************************************************************************************************
   SUBROUTINE create_colvar_xyz_od_section(section)
      TYPE(section_type), POINTER                        :: section

      TYPE(keyword_type), POINTER                        :: keyword
      TYPE(section_type), POINTER                        :: subsection

      CPASSERT(.NOT. ASSOCIATED(section))
      CALL section_create(section, __LOCATION__, name="XYZ_OUTERDIAG", &
                          description="Section to define the cross term (XA-XA(0))*(XB-XB(0))+(XA-XA(0))*(YB-YB(0))"// &
                          " or part of its components as a collective variable. The final term is given by the product"// &
                          " of the components of A with the components of B.", &
                          n_keywords=1, n_subsections=0, repeats=.FALSE.)
      NULLIFY (keyword, subsection)

      CALL keyword_create(keyword, __LOCATION__, name="ATOMS", &
                          variants=(/"POINTS"/), &
                          description="Specifies the index of the atoms/points A and B.", &
                          usage="ATOMS {integer} {integer}", &
                          n_var=2, type_of_var=integer_t)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="COMPONENT_A", &
                          description="Define the component of the position vector which will be used "// &
                          "as a colvar for atom A.", &
                          usage="AXIS (XYZ | X | Y | Z | XY| XZ | YZ)", &
                          enum_c_vals=s2a("XYZ", "X", "Y", "Z", "XY", "XZ", "YZ"), &
                          enum_i_vals=(/do_clv_xyz, do_clv_x, do_clv_y, do_clv_z, do_clv_xy, do_clv_xz, do_clv_yz/), &
                          default_i_val=do_clv_xyz)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="COMPONENT_B", &
                          description="Define the component of the position vector which will be used "// &
                          "as a colvar for atom B.", &
                          usage="AXIS (XYZ | X | Y | Z | XY| XZ | YZ)", &
                          enum_c_vals=s2a("XYZ", "X", "Y", "Z", "XY", "XZ", "YZ"), &
                          enum_i_vals=(/do_clv_xyz, do_clv_x, do_clv_y, do_clv_z, do_clv_xy, do_clv_xz, do_clv_yz/), &
                          default_i_val=do_clv_xyz)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="PBC", &
                          description="Whether periodic boundary conditions should be applied on the "// &
                          "atomic position before computing the colvar or not.", &
                          usage="PBC", &
                          default_l_val=.TRUE., lone_keyword_l_val=.TRUE.)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      ! Must be present in each colvar and handled properly
      CALL create_point_section(subsection)
      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

   END SUBROUTINE create_colvar_xyz_od_section

! **************************************************************************************************
!> \brief energy as collective variable
!> \param section the section to be created
!> \author Sebastiano Caravati
! **************************************************************************************************
   SUBROUTINE create_colvar_u_section(section)
      TYPE(section_type), POINTER                        :: section

      TYPE(keyword_type), POINTER                        :: keyword
      TYPE(section_type), POINTER                        :: subsection

      CPASSERT(.NOT. ASSOCIATED(section))
      CALL section_create(section, __LOCATION__, name="u", &
                          description="Section to define the energy as a generalized collective variable.", &
                          n_keywords=0, n_subsections=0, repeats=.FALSE.)

      NULLIFY (subsection, keyword)
      CALL section_create(subsection, __LOCATION__, name="MIXED", &
                          description="This section allows to use any function of the energy subsystems"// &
                          " in a mixed_env calculation as a collective variable.", &
                          n_keywords=1, n_subsections=0, repeats=.FALSE.)

      CALL keyword_create(keyword, __LOCATION__, name="ENERGY_FUNCTION", &
                          description="Specifies the functional form of the collective variable in mathematical notation.", &
                          usage="ENERGY_FUNCTION (E1+E2-LOG(E1/E2))", type_of_var=lchar_t, &
                          n_var=1)
      CALL section_add_keyword(subsection, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="VARIABLES", &
                          description="Defines the variables of the functional form. To allow an efficient"// &
                          " mapping the order of the energy variables will be considered identical to the"// &
                          " order of the force_eval in the force_eval_order list.", &
                          usage="VARIABLES x", type_of_var=char_t, &
                          n_var=-1)
      CALL section_add_keyword(subsection, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="PARAMETERS", &
                          description="Defines the parameters of the functional form", &
                          usage="PARAMETERS a b D", type_of_var=char_t, &
                          n_var=-1, repeats=.TRUE.)
      CALL section_add_keyword(subsection, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="VALUES", &
                          description="Defines the values of parameter of the functional form", &
                          usage="VALUES ", type_of_var=real_t, &
                          n_var=-1, repeats=.TRUE., unit_str="internal_cp2k")
      CALL section_add_keyword(subsection, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="UNITS", &
                          description="Optionally, allows to define valid CP2K unit strings for each parameter value. "// &
                          "It is assumed that the corresponding parameter value is specified in this unit.", &
                          usage="UNITS angstrom eV*angstrom^-1 angstrom^1 K", type_of_var=char_t, &
                          n_var=-1, repeats=.TRUE.)
      CALL section_add_keyword(subsection, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="DX", &
                          description="Parameter used for computing the derivative with the Ridders' method.", &
                          usage="DX <REAL>", default_r_val=0.1_dp, unit_str="bohr")
      CALL section_add_keyword(subsection, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="ERROR_LIMIT", &
                          description="Checks that the error in computing the derivative is not larger than "// &
                          "the value set; in case error is larger a warning message is printed.", &
                          usage="ERROR_LIMIT <REAL>", default_r_val=1.0E-12_dp)
      CALL section_add_keyword(subsection, keyword)
      CALL keyword_release(keyword)

      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

   END SUBROUTINE create_colvar_u_section

! **************************************************************************************************
!> \brief creates the colvar section regarded to the collective variables distance
!>      of a point from a plane
!> \param section the section to be created
!> \author teo
! **************************************************************************************************
   SUBROUTINE create_colvar_d_pl_section(section)
      TYPE(section_type), POINTER                        :: section

      TYPE(keyword_type), POINTER                        :: keyword
      TYPE(section_type), POINTER                        :: subsection

      CPASSERT(.NOT. ASSOCIATED(section))
      CALL section_create(section, __LOCATION__, name="distance_point_plane", &
                          description="Section to define the distance of a point from a plane "// &
                          "as a collective variables.", &
                          n_keywords=1, n_subsections=0, repeats=.FALSE.)
      NULLIFY (keyword, subsection)

      CALL keyword_create(keyword, __LOCATION__, name="PBC", &
                          description="Whether periodic boundary conditions should be applied on the "// &
                          "atomic position before computing the colvar or not.", &
                          usage="PBC", &
                          default_l_val=.TRUE., lone_keyword_l_val=.TRUE.)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="ATOMS_PLANE", &
                          variants=(/"POINTS_PLANE"/), &
                          description="Specifies the indexes of atoms/points defining the plane.", &
                          usage="ATOMS_PLANE <INTEGER> <INTEGER> <INTEGER>", &
                          n_var=3, type_of_var=integer_t)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="ATOM_POINT", &
                          variants=(/"POINT_POINT"/), &
                          description="Specifies the atom/point index defining the point.", &
                          usage="ATOM_POINT <INTEGER>", &
                          n_var=1, type_of_var=integer_t)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      ! Must be present in each colvar and handled properly
      CALL create_point_section(subsection)
      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

   END SUBROUTINE create_colvar_d_pl_section

! **************************************************************************************************
!> \brief creates the colvar section regarded to the collective variables
!>      angles betweem two planes
!> \param section the section to be created
!> \author teo
! **************************************************************************************************
   SUBROUTINE create_colvar_a_pl_section(section)
      TYPE(section_type), POINTER                        :: section

      TYPE(keyword_type), POINTER                        :: keyword
      TYPE(section_type), POINTER                        :: subsection

      CPASSERT(.NOT. ASSOCIATED(section))
      CALL section_create(section, __LOCATION__, name="angle_plane_plane", &
                          description="This section defines the angle between two planes "// &
                          "as a collective variables.", &
                          n_keywords=1, n_subsections=0, repeats=.FALSE.)
      NULLIFY (keyword, subsection)

      CALL section_create(subsection, __LOCATION__, name="PLANE", &
                          description="This section defines the plane. When using this colvar, "// &
                          "two plane section must be defined!", &
                          n_keywords=1, n_subsections=0, repeats=.TRUE.)

      CALL keyword_create(keyword, __LOCATION__, name="DEF_TYPE", &
                          description="Specify how the plane is defined: either by 3 atoms or by a fixed normal "// &
                          "vector. At least one plane must be defined through atoms.", &
                          usage="DEF_TYPE ATOMS", &
                          default_i_val=plane_def_atoms, &
                          enum_c_vals=s2a("ATOMS", "VECTOR"), &
                          enum_desc=s2a("Plane defined by the position of 3 atoms", &
                                        "Plane defined by a fixed normal vector"), &
                          enum_i_vals=(/plane_def_atoms, plane_def_vec/))
      CALL section_add_keyword(subsection, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="ATOMS", &
                          description="Specifies the indexes of 3 atoms/points defining the plane.", &
                          usage="ATOMS <INTEGER> <INTEGER> <INTEGER>", &
                          n_var=3, type_of_var=integer_t)
      CALL section_add_keyword(subsection, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="NORMAL_VECTOR", &
                          description="Alternatively to 3 atoms/points one can define one of the two, "// &
                          "planes by defining its NORMAL vector.", &
                          usage="NORMAL_VECTOR 0.0 1.0 0.0", &
                          n_var=3, type_of_var=real_t)
      CALL section_add_keyword(subsection, keyword)
      CALL keyword_release(keyword)
      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

      ! Must be present in each colvar and handled properly
      CALL create_point_section(subsection)
      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)
   END SUBROUTINE create_colvar_a_pl_section

! **************************************************************************************************
!> \brief create a geometrical point as a function of several atom coordinates
!> \param section the section to be created
!> \author teo
! **************************************************************************************************
   SUBROUTINE create_point_section(section)
      TYPE(section_type), POINTER                        :: section

      TYPE(keyword_type), POINTER                        :: keyword

      CPASSERT(.NOT. ASSOCIATED(section))
      CALL section_create(section, __LOCATION__, name="POINT", &
                          description="Enables the possibility to use geometrical centers instead of single atoms"// &
                          " to define colvars", &
                          n_keywords=1, n_subsections=0, repeats=.TRUE.)

      NULLIFY (keyword)

      CALL keyword_create(keyword, __LOCATION__, name="TYPE", &
                          description="Chooses the type of geometrical point", &
                          usage="type (GEO_CENTER|FIX_POINT)", &
                          enum_c_vals=s2a("GEO_CENTER", "FIX_POINT"), &
                          enum_desc=s2a("Computes the geometrical center of the listed atoms", &
                                        "Defines a fixed point in space"), &
                          enum_i_vals=(/do_clv_geo_center, do_clv_fix_point/), &
                          default_i_val=do_clv_geo_center)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="ATOMS", &
                          description="Specifies the indexes of atoms defining the geometrical center", &
                          usage="ATOMS {integer} {integer} {integer} {integer}", &
                          n_var=-1, type_of_var=integer_t, repeats=.TRUE.)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create( &
         keyword, __LOCATION__, name="WEIGHTS", &
         description="Specifies the weights for a weighted geometrical center. Default is 1/natoms for every atom", &
         usage="WEIGHTS {real} {real} {real} {real}", &
         n_var=-1, type_of_var=real_t, repeats=.TRUE.)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="XYZ", &
                          description="Specifies the xyz of the fixed point (if the case)", &
                          usage="XYZ {real} {real} {real}", &
                          n_var=3, type_of_var=real_t, unit_str="bohr", &
                          repeats=.FALSE.)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

   END SUBROUTINE create_point_section

! **************************************************************************************************
!> \brief collective variables specifying torsion
!> \param section the section to be created
!> \author teo
! **************************************************************************************************
   SUBROUTINE create_colvar_qparm_section(section)
      TYPE(section_type), POINTER                        :: section

      TYPE(keyword_type), POINTER                        :: keyword
      TYPE(section_type), POINTER                        :: subsection

      CPASSERT(.NOT. ASSOCIATED(section))
      CALL section_create(section, __LOCATION__, name="qparm", &
                          description="Section to define the Q parameter (crystalline order parameter) as a collective variable.", &
                          n_keywords=1, n_subsections=0, repeats=.FALSE.)

      NULLIFY (keyword, subsection)

      CALL keyword_create(keyword, __LOCATION__, name="ATOMS_FROM", &
                          variants=(/"POINTS_FROM"/), &
                          description="Specify indexes of atoms/points building the coordination variable. ", &
                          usage="ATOMS_FROM {integer} {integer} ..", repeats=.TRUE., &
                          n_var=-1, type_of_var=integer_t)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="ATOMS_TO", &
                          variants=(/"POINTS_TO"/), &
                          description="Specify indexes of atoms/points building the coordination variable. ", &
                          usage="ATOMS_TO {integer} {integer} ..", repeats=.TRUE., &
                          n_var=-1, type_of_var=integer_t)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="RCUT", &
                          description="Specifies the distance cutoff for neighbors. "// &
                          "Cutoff function is exactly zero for all neighbors beyond RCUT.", &
                          usage="RCUT {real}", &
                          n_var=1, unit_str="angstrom", type_of_var=real_t)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="INCLUDE_IMAGES", &
                          description="Whether to include periodic images of ATOMS_TO into the neighbor list.", &
                          usage="INCLUDE_IMAGES", &
                          default_l_val=.FALSE., lone_keyword_l_val=.TRUE.)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="RSTART", &
                          description="Specifies the distance cutoff for neighbors. "// &
                          "Cutoff function is exactly 1 for all neighbors closer than RSTART.", &
                          usage="RSTART {real}", &
                          n_var=1, unit_str="angstrom", type_of_var=real_t)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="L", &
                          description="Specifies the L spherical harmonics from Ylm.", &
                          usage="L {integer}", &
                          n_var=1, type_of_var=integer_t)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      !CALL keyword_create(keyword, __LOCATION__, name="ALPHA", &
      !                    description="Specifies the width of the Fermi-Dirac style smearing around RCUT.", &
      !                    usage="ALPHA {real}", unit_str="angstrom^-1", default_r_val=0.0_dp)
      !CALL section_add_keyword(section, keyword)
      !CALL keyword_release(keyword)

      ! Must be present in each colvar and handled properly
      CALL create_point_section(subsection)
      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

   END SUBROUTINE create_colvar_qparm_section

! **************************************************************************************************
!> \brief collective variables specifying hydronium solvation
!> \param section the section to be created
!> \author Marcel Baer
! **************************************************************************************************
   SUBROUTINE create_colvar_hydronium_shell_section(section)
      TYPE(section_type), POINTER                        :: section

      TYPE(keyword_type), POINTER                        :: keyword

      CPASSERT(.NOT. ASSOCIATED(section))
      CALL section_create(section, __LOCATION__, name="HYDRONIUM_SHELL", &
                          description="Section to define the formation of a hydronium as a"// &
                          " collective variable. Number of oxygens in the 1st shell of the"// &
                          " hydronium. Adapted from Equation (3) in Supplementary Info of"// &
                          " J. Am. Chem. Soc.,128, 2006, 11318, i.e. omitting the cutoff function"// &
                          " and summing only over the oxygens of water.", &
                          n_keywords=1, n_subsections=0, repeats=.FALSE.)

      NULLIFY (keyword)

      CALL keyword_create(keyword, __LOCATION__, name="OXYGENS", &
                          description="Specifies indexes of atoms building the coordination variable."// &
                          " Oxygens of the water molecules.", &
                          usage="OXYGENS {integer} {integer} ..", repeats=.TRUE., &
                          n_var=-1, type_of_var=integer_t)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="HYDROGENS", &
                          description="Specifies indexes of atoms building the coordination variable."// &
                          " Hydrogens of the water molecules.", &
                          usage="HYDROGENS {integer} {integer} ..", repeats=.TRUE., &
                          n_var=-1, type_of_var=integer_t)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="ROO", &
                          description="Specifies the rc parameter in the coordination function:"// &
                          " number of oxygens per water oxygen.", &
                          usage="ROO {real}", default_r_val=cp_unit_to_cp2k(value=3.0_dp, &
                                                                            unit_str="bohr"), unit_str="bohr", n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="pOO", &
                          variants=(/"EXPON_NUMERATORA"/), &
                          description="Sets the value of the numerator of the exponential factor"// &
                          " in the coordination function: number of oxygens per water oxygen.", &
                          usage="pOO {integer}", default_i_val=6, &
                          n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="qOO", &
                          variants=(/"EXPON_DENOMINATORA"/), &
                          description="Sets the value of the denominator of the exponential factor"// &
                          " in the coordination function: number of oxygens per water oxygen.", &
                          usage="qOO {integer}", default_i_val=12, &
                          n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="ROH", &
                          description="Specifies the rc parameter in the coordination function:"// &
                          " number of hydrogens per water molecule.", &
                          usage="ROH {real}", default_r_val=cp_unit_to_cp2k(value=3.0_dp, &
                                                                            unit_str="bohr"), unit_str="bohr", n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="pOH", &
                          variants=(/"EXPON_NUMERATORB"/), &
                          description="Sets the value of the numerator of the exponential factor"// &
                          " in the coordination function: number of hydrogens per water molecule.", &
                          usage="pOH {integer}", default_i_val=6, &
                          n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="qOH", &
                          variants=(/"EXPON_DENOMINATORB"/), &
                          description="Sets the value of the denominator of the exponential factor"// &
                          " in the coordination function: number of hydrogens per water molecule.", &
                          usage="qOH {integer}", default_i_val=12, &
                          n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="NH", &
                          description="Specifies the NH parameter in the M function.", &
                          usage="NH {real}", default_r_val=3.0_dp, &
                          n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="pM", &
                          variants=(/"EXPON_NUMERATOR"/), &
                          description="Sets the value of the numerator of the exponential factor"// &
                          " in the M function.", &
                          usage="pM {integer}", default_i_val=8, &
                          n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="qM", &
                          variants=(/"EXPON_DENOMINATOR"/), &
                          description="Sets the value of the denominator of the exponential factor"// &
                          " in the M function.", &
                          usage="qM {integer}", default_i_val=16, &
                          n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="LAMBDA", &
                          description="Specify the LAMBDA parameter in the hydronium function.", &
                          usage="LAMBDA {real}", default_r_val=10.0_dp, &
                          n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

   END SUBROUTINE create_colvar_hydronium_shell_section

! **************************************************************************************************
!> \brief collective variables specifying the distance between hydronium and hydroxide ion
!> \param section the section to be created
!> \author Dorothea Golze
! **************************************************************************************************
   SUBROUTINE create_colvar_hydronium_dist_section(section)
      TYPE(section_type), POINTER                        :: section

      TYPE(keyword_type), POINTER                        :: keyword

      CPASSERT(.NOT. ASSOCIATED(section))
      CALL section_create(section, __LOCATION__, name="HYDRONIUM_DISTANCE", &
                          description="Section to define the formation of a hydronium as a"// &
                          " collective variable. Distance between hydronium and hydroxide ion"// &
                          " Experimental at this point, i.e. not proved to be an effective"// &
                          " collective variable.", &
                          n_keywords=1, n_subsections=0, repeats=.FALSE.)

      NULLIFY (keyword)

      CALL keyword_create(keyword, __LOCATION__, name="OXYGENS", &
                          description="Specifies indexes of atoms building the coordination variable."// &
                          " Oxygens of the water molecules.", &
                          usage="OXYGENS {integer} {integer} ..", repeats=.TRUE., &
                          n_var=-1, type_of_var=integer_t)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="HYDROGENS", &
                          description="Specifies indexes of atoms building the coordination variable."// &
                          " Hydrogens of the water molecules.", &
                          usage="HYDROGENS {integer} {integer} ..", repeats=.TRUE., &
                          n_var=-1, type_of_var=integer_t)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="ROH", &
                          description="Specifies the rc parameter in the coordination function:"// &
                          " number of hydrogens per water molecule.", &
                          usage="ROH {real}", default_r_val=cp_unit_to_cp2k(value=2.4_dp, &
                                                                            unit_str="bohr"), unit_str="bohr", n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="pOH", &
                          description="Sets the value of the numerator of the exponential factor"// &
                          " in the coordination function: number of hydrogens per water molecule.", &
                          usage="pOH {integer}", default_i_val=6, &
                          n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="qOH", &
                          description="Sets the value of the denominator of the exponential factor"// &
                          " in the coordination function: number of hydrogens per water molecule.", &
                          usage="qOH {integer}", default_i_val=12, &
                          n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="NH", &
                          description="Specifies the NH parameter in the M function.", &
                          usage="NH {real}", default_r_val=2.2_dp, &
                          n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="pM", &
                          description="Sets the value of the numerator of the exponential factor"// &
                          " in the M function.", &
                          usage="pM {integer}", default_i_val=8, &
                          n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="qM", &
                          description="Sets the value of the denominator of the exponential factor"// &
                          " in the M function.", &
                          usage="qM {integer}", default_i_val=16, &
                          n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="NN", &
                          description="Specifies the NN parameter in the F function.", &
                          usage="NN {real}", default_r_val=1.5_dp, &
                          n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="pF", &
                          description="Sets the value of the numerator of the exponential factor"// &
                          " in the F function.", &
                          usage="pF {integer}", default_i_val=8, &
                          n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="qF", &
                          description="Sets the value of the denominator of the exponential factor"// &
                          " in the F function.", &
                          usage="qF {integer}", default_i_val=16, &
                          n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="LAMBDA", &
                          description="Specify the LAMBDA parameter in the hydronium function.", &
                          usage="LAMBDA {real}", default_r_val=20.0_dp, &
                          n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

   END SUBROUTINE create_colvar_hydronium_dist_section

! **************************************************************************************************
!> \brief collective variables specifying the solvation of carboxylic acid;
!>        distance between hydronium ion and acetate ion; Equation (2) in
!>        Supplementary Information of J. Am. Chem. Soc.,128,  2006, 11318
!> \param section the section to be created
!> \author Dorothea Golze
! **************************************************************************************************
   SUBROUTINE create_colvar_acid_hyd_dist_section(section)
      TYPE(section_type), POINTER                        :: section

      TYPE(keyword_type), POINTER                        :: keyword

      CPASSERT(.NOT. ASSOCIATED(section))
      CALL section_create(section, __LOCATION__, name="ACID_HYDRONIUM_DISTANCE", &
                          description="Section to define the dissociation of a carboxylic acid in"// &
                          " water. Distance between hydronium ion and acetate ion. Equation (2)"// &
                          " in Supplementary Info of J. Am. Chem. Soc.,128,  2006, 11318.", &
                          n_keywords=1, n_subsections=0, repeats=.FALSE.)

      NULLIFY (keyword)

      CALL keyword_create(keyword, __LOCATION__, name="OXYGENS_WATER", &
                          description="Specifies indexes of atoms building the coordination variable."// &
                          " Oxygens of the water molecules. ", &
                          usage="OXYGENS {integer} {integer} ..", repeats=.TRUE., &
                          n_var=-1, type_of_var=integer_t)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="OXYGENS_ACID", &
                          description="Specifies indexes of atoms building the coordination variable."// &
                          " Oxygens of the carboxyl groups.", &
                          usage="OXYGENS {integer} {integer} ..", repeats=.TRUE., &
                          n_var=-1, type_of_var=integer_t)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="HYDROGENS", &
                          description="Specifies indexes of atoms building the coordination variable."// &
                          " Hydrogens of the water molecules and of the carboxyl groups.", &
                          usage="HYDROGENS {integer} {integer} ..", repeats=.TRUE., &
                          n_var=-1, type_of_var=integer_t)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="pWOH", &
                          description="Sets the value of the numerator of the exponential factor"// &
                          " in the coordination function: number of hydrogens per water molecule.", &
                          usage="pWOH {integer}", default_i_val=8, &
                          n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="qWOH", &
                          description="Sets the value of the denominator of the exponential factor"// &
                          " in the coordination function: number of hydrogens per water molecule.", &
                          usage="qWOH {integer}", default_i_val=16, &
                          n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="RWOH", &
                          description="Specify the rc parameter in the coordination function:"// &
                          " number of hydrogens per water molecule.", &
                          usage="RWOH {real}", default_r_val=cp_unit_to_cp2k(value=2.4_dp, &
                                                                             unit_str="bohr"), unit_str="bohr", n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="pAOH", &
                          description="Sets the value of the numerator of the exponential factor"// &
                          " in the coordination function: number of hydrogens per carboxyl group.", &
                          usage="pAOH {integer}", default_i_val=6, &
                          n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="qAOH", &
                          description="Sets the value of the denominator of the exponential factor"// &
                          " in the coordination function: number of hydrogens per carboxyl group.", &
                          usage="qAOH {integer}", default_i_val=14, &
                          n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="RAOH", &
                          description="Specify the rc parameter in the coordination function:"// &
                          " number of hydrogens per carboxyl group.", &
                          usage="RAOH {real}", default_r_val=cp_unit_to_cp2k(value=2.4_dp, &
                                                                             unit_str="bohr"), unit_str="bohr", n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="pCUT", &
                          description="Sets the value of the numerator of the exponential factor"// &
                          " in the cutoff function.", &
                          usage="pCUT {integer}", default_i_val=6, &
                          n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="qCUT", &
                          description="Sets the value of the denominator of the exponential factor"// &
                          " in the cutoff function.", &
                          usage="qCUT {integer}", default_i_val=12, &
                          n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="NC", &
                          description="Specifies the NC parameter in the cutoff function.", &
                          usage="NC {real}", default_r_val=0.56_dp, &
                          n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="LAMBDA", &
                          variants=(/"LAMBDA"/), &
                          description="Specifies the LAMBDA parameter carboxylic acid function.", &
                          usage="LAMBDA {real}", default_r_val=20.0_dp, &
                          n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

   END SUBROUTINE create_colvar_acid_hyd_dist_section

! **************************************************************************************************
!> \brief collective variables specifying the solvation of carboxylic acid;
!>        number of oxygens in the 1st shell of the hydronium; Equation (3) in
!>        Supplementary Information of J. Am. Chem. Soc.,128,  2006, 11318
!> \param section the section to be created
!> \author Dorothea Golze
! **************************************************************************************************
   SUBROUTINE create_colvar_acid_hyd_shell_section(section)
      TYPE(section_type), POINTER                        :: section

      TYPE(keyword_type), POINTER                        :: keyword

      CPASSERT(.NOT. ASSOCIATED(section))
      CALL section_create(section, __LOCATION__, name="ACID_HYDRONIUM_SHELL", &
                          description="Section to define the dissociation of a carboxylic acid in"// &
                          " water. Number of oxygens in the 1st shell of the hydronium. Equation (3)"// &
                          " in Supplementary Info of J. Am. Chem. Soc.,128,  2006, 11318. Similar to"// &
                          " the HYDRONIUM colvar, but with modification for the acid.", &
                          n_keywords=1, n_subsections=0, repeats=.FALSE.)

      NULLIFY (keyword)

      CALL keyword_create(keyword, __LOCATION__, name="OXYGENS_WATER", &
                          description="Specifies indexes of atoms building the coordination variable."// &
                          " Oxygens of the water molecules. ", &
                          usage="OXYGENS {integer} {integer} ..", repeats=.TRUE., &
                          n_var=-1, type_of_var=integer_t)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="OXYGENS_ACID", &
                          description="Specifies indexes of atoms building the coordination variable."// &
                          " Oxygens of the carboxyl groups.", &
                          usage="OXYGENS {integer} {integer} ..", repeats=.TRUE., &
                          n_var=-1, type_of_var=integer_t)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="HYDROGENS", &
                          description="Specifies indexes of atoms building the coordination variable."// &
                          " Hydrogens of the water molecules and of the carboxyl groups.", &
                          usage="HYDROGENS {integer} {integer} ..", repeats=.TRUE., &
                          n_var=-1, type_of_var=integer_t)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="pWOH", &
                          description="Sets the value of the numerator of the exponential factor"// &
                          " in the coordination function: number of hydrogens per water molecule.", &
                          usage="pWOH {integer}", default_i_val=8, &
                          n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="qWOH", &
                          description="Sets the value of the denominator of the exponential factor"// &
                          " in the coordination function: number of hydrogens per water molecule.", &
                          usage="qWOH {integer}", default_i_val=16, &
                          n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="RWOH", &
                          description="Specifies the rc parameter in the coordination function:"// &
                          " number of hydrogens per water molecule.", &
                          usage="RWOH {real}", default_r_val=cp_unit_to_cp2k(value=2.4_dp, &
                                                                             unit_str="bohr"), unit_str="bohr", n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="pAOH", &
                          description="Sets the value of the numerator of the exponential factor"// &
                          " in the coordination function: number of hydrogens per carboxyl group.", &
                          usage="pAOH {integer}", default_i_val=6, &
                          n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="qAOH", &
                          description="Sets the value of the denominator of the exponential factor"// &
                          " in the coordination function: number of hydrogens per carboxyl group.", &
                          usage="qAOH {integer}", default_i_val=14, &
                          n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="RAOH", &
                          description="Specifies the rc parameter in the coordination function:"// &
                          " number of hydrogens per carboxyl group.", &
                          usage="RAOH {real}", default_r_val=cp_unit_to_cp2k(value=2.4_dp, &
                                                                             unit_str="bohr"), unit_str="bohr", n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="pOO", &
                          description="Sets the value of the numerator of the exponential factor"// &
                          " in the coordination function: number of oxygens per water oxygen.", &
                          usage="pOO {integer}", default_i_val=6, &
                          n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="qOO", &
                          description="Sets the value of the denominator of the exponential factor"// &
                          " in the coordination function: number of oxygens per water oxygen.", &
                          usage="qOO {integer}", default_i_val=12, &
                          n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="ROO", &
                          description="Specifies the rc parameter in the coordination function:"// &
                          " number of oxygens per water oxygen.", &
                          usage="ROO {real}", default_r_val=cp_unit_to_cp2k(value=5.5_dp, &
                                                                            unit_str="bohr"), unit_str="bohr", n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="pM", &
                          description="Sets the value of the numerator of the exponential factor"// &
                          " in the M function.", &
                          usage="pM {integer}", default_i_val=8, &
                          n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="qM", &
                          description="Sets the value of the denominator of the exponential factor"// &
                          " in the M function.", &
                          usage="qM {integer}", default_i_val=16, &
                          n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="NH", &
                          description="Specifies the NH parameter in the M function.", &
                          usage="NH {real}", default_r_val=2.2_dp, &
                          n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="pCUT", &
                          description="Sets the value of the numerator of the exponential factor"// &
                          " in the cutoff function.", &
                          usage="pCUT {integer}", default_i_val=6, &
                          n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="qCUT", &
                          description="Sets the value of the denominator of the exponential factor"// &
                          " in the cutoff function.", &
                          usage="qCUT {integer}", default_i_val=12, &
                          n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="NC", &
                          description="Specifies the NC parameter in the cutoff function.", &
                          usage="NC {real}", default_r_val=0.9_dp, &
                          n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="LAMBDA", &
                          variants=(/"LAMBDA"/), &
                          description="Specifies the LAMBDA parameter carboxylic acid function.", &
                          usage="LAMBDA {real}", default_r_val=10.0_dp, &
                          n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

   END SUBROUTINE create_colvar_acid_hyd_shell_section

! **************************************************************************************************
!> \brief ...
!> \param section ...
! **************************************************************************************************
   SUBROUTINE create_colvar_rmsd_section(section)
      TYPE(section_type), POINTER                        :: section

      TYPE(keyword_type), POINTER                        :: keyword
      TYPE(section_type), POINTER                        :: subsection, subsubsection

      CPASSERT(.NOT. ASSOCIATED(section))
      CALL section_create(section, __LOCATION__, name="rmsd", &
                          description="Section to define a CV as function of RMSD computed with respect to"// &
                          " given reference configurations. For 2 configurations the colvar is equal to:"// &
                          " ss = (RMSDA-RMSDB)/(RMSDA+RMSDB), while if only 1 configuration is given, then the"// &
                          " colvar is just the RMSD from that frame.", &
                          n_keywords=1, n_subsections=0, repeats=.FALSE.)

      NULLIFY (keyword, subsection, subsubsection)
      CALL keyword_create(keyword, __LOCATION__, name="SUBSET_TYPE", &
                          description="Define the subsytem used to compute the RMSD", &
                          usage="SUBSET_TYPE ALL", &
                          enum_c_vals=s2a("ALL", "LIST", "WEIGHT_LIST"), &
                          enum_i_vals=(/rmsd_all, rmsd_list, rmsd_weightlist/), &
                          default_i_val=rmsd_all)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="ALIGN_FRAMES", &
                          description="Whether the reference frames should be aligned to minimize the RMSD", &
                          usage="ALIGN_FRAME", &
                          default_l_val=.FALSE., lone_keyword_l_val=.TRUE.)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="ATOMS", &
                          description="Specify indexes of atoms building the subset. ", &
                          usage="ATOMS {integer} {integer} ..", repeats=.TRUE., &
                          n_var=-1, type_of_var=integer_t)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="WEIGHTS", &
                          description="Specify weights of atoms building the subset. ", &
                          usage="weightS {real} {real} ..", repeats=.TRUE., &
                          n_var=-1, type_of_var=real_t)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL section_create(subsection, __LOCATION__, name="FRAME", &
                          description="Specify coordinates of the frame (number of frames can be either 1 or 2)", &
                          repeats=.TRUE.)

      CALL keyword_create(keyword, __LOCATION__, name="COORD_FILE_NAME", &
                          description="Name of the xyz file with coordinates (alternative to &COORD section)", &
                          usage="COORD_FILE_NAME <CHAR>", &
                          default_lc_val="")
      CALL section_add_keyword(subsection, keyword)
      CALL keyword_release(keyword)

      CALL create_coord_section_cv(subsubsection, "RMSD")
      CALL section_add_subsection(subsection, subsubsection)
      CALL section_release(subsubsection)

      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

   END SUBROUTINE create_colvar_rmsd_section

! **************************************************************************************************
!> \brief collective variables specifying the space orthogonal to the reaction path
!>        in the space spanned by the involved collective coordinates
!> \param section the section to be created
!> \author fschiff
! **************************************************************************************************
   SUBROUTINE create_colvar_rpath_section(section)
      TYPE(section_type), POINTER                        :: section

      CPASSERT(.NOT. ASSOCIATED(section))
      CALL section_create(section, __LOCATION__, name="REACTION_PATH", &
                          description="Section defining a one dimensional reaction path in an Q-dimensional space of colvars. "// &
                          "Constraining this colvar, allows to sample the space orthogonal to the reaction path, "// &
                          "both in the Q-dimensional colvar and 3N-Q remaining coordinates. "// &
                          "For the details of the function see cited literature.", &
                          n_keywords=1, n_subsections=0, repeats=.FALSE., &
                          citations=(/Branduardi2007/))

      CALL keywords_colvar_path(section)
   END SUBROUTINE create_colvar_rpath_section

! **************************************************************************************************
!> \brief Distance from reaction path
!> \param section the section to be created
!> \author 01.2010
! **************************************************************************************************
   SUBROUTINE create_colvar_dpath_section(section)
      TYPE(section_type), POINTER                        :: section

      CPASSERT(.NOT. ASSOCIATED(section))
      CALL section_create(section, __LOCATION__, name="DISTANCE_FROM_PATH", &
                          description="Section defining the distance from a one dimensional reaction "// &
                          "path in an Q-dimensional space of colvars. "// &
                          "Constraining this colvar, allows to sample the space equidistant to the reaction path, "// &
                          "both in the Q-dimensional colvar and 3N-Q remaining coordinates. "// &
                          "For the details of the function see cited literature.", &
                          n_keywords=1, n_subsections=0, repeats=.FALSE., &
                          citations=(/Branduardi2007/))

      CALL keywords_colvar_path(section)
   END SUBROUTINE create_colvar_dpath_section

! **************************************************************************************************
!> \brief Section describinf keywords for both reaction path and distance from reaction path
!> \param section the section to be created
!> \author 01.2010
! **************************************************************************************************
   SUBROUTINE keywords_colvar_path(section)

      TYPE(section_type), POINTER                        :: section

      TYPE(keyword_type), POINTER                        :: keyword
      TYPE(section_type), POINTER                        :: print_key, subsection, subsubsection

      NULLIFY (keyword, subsection, subsubsection, print_key)
      CALL create_colvar_section(subsection, skip_recursive_colvar=.TRUE.)
      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

      CALL keyword_create(keyword, __LOCATION__, name="DISTANCES_RMSD", &
                          description=" ", &
                          usage="DISTANCES_RMSD T", &
                          default_l_val=.FALSE., lone_keyword_l_val=.TRUE.)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="RMSD", &
                          description=" ", &
                          usage="RMSD T", &
                          default_l_val=.FALSE., lone_keyword_l_val=.TRUE.)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="SUBSET_TYPE", &
                          description="Define the subsytem used to compute the RMSD", &
                          usage="SUBSET_TYPE ALL", &
                          enum_c_vals=s2a("ALL", "LIST"), &
                          enum_i_vals=(/rmsd_all, rmsd_list/), &
                          default_i_val=rmsd_all)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="ALIGN_FRAMES", &
                          description="Whether the reference frames should be aligned to minimize the RMSD", &
                          usage="ALIGN_FRAME", &
                          default_l_val=.FALSE., lone_keyword_l_val=.TRUE.)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="ATOMS", &
                          description="Specify indexes of atoms building the subset. ", &
                          usage="ATOMS {integer} {integer} ..", repeats=.TRUE., &
                          n_var=-1, type_of_var=integer_t)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL section_create(subsection, __LOCATION__, name="FRAME", &
                          description="Specify coordinates of the frame", &
                          repeats=.TRUE.)

      CALL keyword_create(keyword, __LOCATION__, name="COORD_FILE_NAME", &
                          description="Name of the xyz file with coordinates (alternative to &COORD section)", &
                          usage="COORD_FILE_NAME <CHAR>", &
                          default_lc_val="")
      CALL section_add_keyword(subsection, keyword)
      CALL keyword_release(keyword)

      CALL create_coord_section_cv(subsubsection, "RMSD")
      CALL section_add_subsection(subsection, subsubsection)
      CALL section_release(subsubsection)

      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

      CALL keyword_create(keyword, __LOCATION__, name="FUNCTION", &
                          description="Specifies the ith element of the vector valued function that defines the reaction path. "// &
                          "This keyword needs to repeat exactly Q times, and the order must match the order of the colvars. "// &
                          "The VARIABLE (e.g. T) which parametrises the curve can be used as the target of a constraint.", &
                          usage="FUNCTION (sin(T+2)+2*T)", type_of_var=lchar_t, &
                          n_var=1, default_lc_val="0", repeats=.TRUE.)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="VARIABLE", &
                          description="Specifies the name of the variable that parametrises the FUNCTION "// &
                          "defining the reaction path.", &
                          usage="VARIABLE T", type_of_var=char_t, &
                          n_var=1, repeats=.FALSE.)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create( &
         keyword, __LOCATION__, name="LAMBDA", &
         description="Specifies the exponent of the Gaussian used in the integral representation of the colvar. "// &
         "The shape of the space orthogonal to the reaction path is defined by this choice. "// &
         "In the limit of large values, it is given by the plane orthogonal to the path. "// &
         "In practice, modest values are required for stable numerical integration.", &
         usage="LAMBDA {real}", &
         type_of_var=real_t, default_r_val=5.0_dp)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="STEP_SIZE", &
                          description="Step size in the numerical integration, "// &
                          "a few thousand points are common, and the proper number also depends on LAMBDA.", &
                          usage="STEP_SIZE {real}", &
                          type_of_var=real_t, default_r_val=0.01_dp)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="RANGE", &
                          description="The range of VARIABLE used for the parametrisation.", &
                          usage="RANGE <REAL> <REAL>", &
                          n_var=2, type_of_var=real_t)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL cp_print_key_section_create( &
         print_key, __LOCATION__, name="MAP", &
         description="Activating this print key will print once a file with the values of the FUNCTION on a grid "// &
         "of COLVAR values in a specified range. "// &
         "GRID_SPACING and RANGE for every COLVAR has to be specified again in the same order as they are in the input.", &
         print_level=high_print_level, filename="PATH")

      CALL keyword_create(keyword, __LOCATION__, name="RANGE", &
                          description="The range of of the grid of the COLVAR.", &
                          usage="RANGE <REAL> <REAL>", &
                          n_var=2, type_of_var=real_t, repeats=.TRUE.)
      CALL section_add_keyword(print_key, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="GRID_SPACING", &
                          description="Distance between two gridpoints for the grid on the COLVAR", &
                          usage="STEP_SIZE {real}", repeats=.TRUE., &
                          type_of_var=real_t, default_r_val=0.01_dp)
      CALL section_add_keyword(print_key, keyword)
      CALL keyword_release(keyword)

      CALL section_add_subsection(section, print_key)
      CALL section_release(print_key)

   END SUBROUTINE keywords_colvar_path

! **************************************************************************************************
!> \brief Colvar allowing a combination of COLVARS
!> \param section the section to be created
!> \author Teodoro Laino [tlaino] - 12.2008
! **************************************************************************************************
   SUBROUTINE create_colvar_comb_section(section)
      TYPE(section_type), POINTER                        :: section

      TYPE(keyword_type), POINTER                        :: keyword
      TYPE(section_type), POINTER                        :: subsection

      CPASSERT(.NOT. ASSOCIATED(section))
      CALL section_create(section, __LOCATION__, name="COMBINE_COLVAR", &
                          description="Allows the possibility to combine several COLVARs into one COLVAR "// &
                          "with a generic function.", &
                          n_keywords=1, n_subsections=0, repeats=.FALSE.)

      NULLIFY (keyword, subsection)
      CALL create_colvar_section(subsection, skip_recursive_colvar=.TRUE.)
      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

      CALL keyword_create(keyword, __LOCATION__, name="FUNCTION", &
                          description="Specifies the function used to combine different COLVARs into one.", &
                          ! **************************************************************************************************
                          !> \brief ...
                          !> \param CV1^2 ...
                          !> \param CV2^2 ...
                          !> \param " ...
                          !> \param type_of_var=lchar_t ...
                          !> \param n_var=1 ...
                          !> \param error=error ...
                          ! **************************************************************************************************
                          usage="FUNCTION SQRT(CV1^2+CV2^2)", type_of_var=lchar_t, &
                          n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="VARIABLES", &
                          description="Specifies the name of the variable that parametrises the FUNCTION "// &
                          "defining how COLVARS should be combined. The matching follows the same order of the "// &
                          "COLVARS definition in the input file.", &
                          usage="VARIABLE CV1 CV2 CV3", type_of_var=char_t, n_var=-1, repeats=.FALSE.)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="PARAMETERS", &
                          description="Defines the parameters of the functional form", &
                          usage="PARAMETERS a b D", type_of_var=char_t, &
                          n_var=-1, repeats=.TRUE.)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="VALUES", &
                          description="Defines the values of  parameter of the functional form", &
                          usage="VALUES ", type_of_var=real_t, &
                          n_var=-1, repeats=.TRUE., unit_str="internal_cp2k")
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="DX", &
                          description="Parameter used for computing the derivative of the combination "// &
                          "of COLVARs with the Ridders' method.", &
                          usage="DX <REAL>", default_r_val=0.1_dp, unit_str="bohr")
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="ERROR_LIMIT", &
                          description="Checks that the error in computing the derivative is not larger than "// &
                          "the value set; in case error is larger a warning message is printed.", &
                          usage="ERROR_LIMIT <REAL>", default_r_val=1.0E-12_dp)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

   END SUBROUTINE create_colvar_comb_section

! **************************************************************************************************
!> \brief Creates the coord section
!> \param section the section to create
!> \param name ...
!> \author teo
! **************************************************************************************************
   SUBROUTINE create_coord_section_cv(section, name)
      TYPE(section_type), POINTER                        :: section
      CHARACTER(LEN=*), INTENT(IN)                       :: name

      TYPE(keyword_type), POINTER                        :: keyword

      CPASSERT(.NOT. ASSOCIATED(section))
      CALL section_create(section, __LOCATION__, name="coord", &
                          description="The positions for "//TRIM(name)//" used for restart", &
                          n_keywords=1, n_subsections=0, repeats=.FALSE.)
      NULLIFY (keyword)

      CALL keyword_create(keyword, __LOCATION__, name="_DEFAULT_KEYWORD_", &
                          description="Specify positions of the system", repeats=.TRUE., &
                          usage="{Real} ...", type_of_var=real_t, n_var=-1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

   END SUBROUTINE create_coord_section_cv

! **************************************************************************************************
!> \brief collective variables specifying h bonds
!> \param section the section to be created
!> \author alin m elena
! **************************************************************************************************
   SUBROUTINE create_colvar_wc_section(section)
      TYPE(section_type), POINTER                        :: section

      TYPE(keyword_type), POINTER                        :: keyword
      TYPE(section_type), POINTER                        :: subsection

      CPASSERT(.NOT. ASSOCIATED(section))
      CALL section_create(section, __LOCATION__, name="wc", &
                          description="Section to define the hbond wannier centre as a collective variables.", &
                          n_keywords=1, n_subsections=0, repeats=.FALSE.)
      NULLIFY (keyword, subsection)

      CALL keyword_create(keyword, __LOCATION__, name="RCUT", &
                          description="Parameter used for computing the cutoff radius for searching "// &
                          "the wannier centres around an atom", &
                          usage="RCUT <REAL>", default_r_val=0.529177208590000_dp, unit_str="angstrom", &
                          type_of_var=real_t, repeats=.FALSE.)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="ATOMS", &
                          variants=(/"POINTS"/), &
                          description="Specifies the indexes of atoms/points defining the bond (Od, H, Oa).", &
                          usage="ATOMS {integer} {integer} {integer}", &
                          n_var=3, type_of_var=integer_t, repeats=.TRUE.)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      ! Must be present in each colvar and handled properly
      CALL create_point_section(subsection)
      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

   END SUBROUTINE create_colvar_wc_section

   ! **************************************************************************************************
!> \brief collective variables specifying h bonds= wire
!> \param section the section to be created
!> \author alin m elena
! **************************************************************************************************
   SUBROUTINE create_colvar_hbp_section(section)
      TYPE(section_type), POINTER                        :: section

      TYPE(keyword_type), POINTER                        :: keyword
      TYPE(section_type), POINTER                        :: subsection

      CPASSERT(.NOT. ASSOCIATED(section))
      CALL section_create(section, __LOCATION__, name="hbp", &
                          description="Section to define the hbond wannier centre as a collective variables.", &
                          n_keywords=1, n_subsections=0, repeats=.FALSE.)
      NULLIFY (keyword, subsection)

      CALL keyword_create(keyword, __LOCATION__, name="RCUT", &
                          description="Parameter used for computing the cutoff radius for searching "// &
                          "the wannier centres around an atom", &
                          usage="RCUT <REAL>", default_r_val=0.529177208590000_dp, unit_str="angstrom", &
                          type_of_var=real_t, repeats=.FALSE.)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="SHIFT", &
                          description="Parameter used for shifting each term in the sum ", &
                          usage="SHIFT <REAL>", default_r_val=0.5_dp, &
                          type_of_var=real_t, repeats=.FALSE.)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="NPOINTS", &
                          description="The number of points in the path", &
                          usage="NPOINTS {integer}", default_i_val=-1, &
                          n_var=1, type_of_var=integer_t, repeats=.FALSE.)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="ATOMS", &
                          variants=(/"POINTS"/), &
                          description="Specifies the indexes of atoms/points defining the bond (Od, H, Oa).", &
                          usage="ATOMS {integer} {integer} {integer}", &
                          n_var=3, type_of_var=integer_t, repeats=.TRUE.)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      ! Must be present in each colvar and handled properly
      CALL create_point_section(subsection)
      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

   END SUBROUTINE create_colvar_hbp_section

! **************************************************************************************************
!> \brief collective variables specifying ring puckering
!> \brief D. Cremer and J.A. Pople, JACS 97 1354 (1975)
!> \param section the section to be created
!> \author Marcel Baer
! **************************************************************************************************
   SUBROUTINE create_colvar_ring_puckering_section(section)
      TYPE(section_type), POINTER                        :: section

      TYPE(keyword_type), POINTER                        :: keyword
      TYPE(section_type), POINTER                        :: subsection

      CPASSERT(.NOT. ASSOCIATED(section))
      CALL section_create(section, __LOCATION__, name="RING_PUCKERING", &
                          description="Section to define general ring puckering collective variables.", &
                          n_keywords=1, n_subsections=0, repeats=.FALSE.)

      NULLIFY (keyword, subsection)

      CALL keyword_create(keyword, __LOCATION__, name="ATOMS", &
                          variants=(/"POINTS"/), &
                          description="Specifies the indexes of atoms/points defining the ring. "// &
                          "At least 4 Atoms are needed.", &
                          usage="ATOMS {integer} {integer} {integer} ..", &
                          n_var=-1, type_of_var=integer_t)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, __LOCATION__, name="COORDINATE", &
                          description="Indicate the coordinate to be used. Follow the Cremer-Pople definition for a N ring. "// &
                          "0 is the total puckering variable Q, "// &
                          "2..[N/2] are puckering coordinates. "// &
                          "-2..-[N/2-1] are puckering angles.", &
                          usage="COORDINATE {integer}", default_i_val=0, &
                          n_var=1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      ! Must be present in each colvar and handled properly
      CALL create_point_section(subsection)
      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

   END SUBROUTINE create_colvar_ring_puckering_section

! **************************************************************************************************

END MODULE input_cp2k_colvar
